add stub function normalize_path to LinuxOS

engine/os/linux/LinuxOS.cpp

@@ -206,6 +206,12 @@ void list_files(const char* path, Vector<DynamicString>& files)
 	closedir(dir);
 }
 
+//-----------------------------------------------------------------------------
+const char* normalize_path(const char* path)
+{
+	// Stub function
+}
+
 //-----------------------------------------------------------------------------
 const char* get_cwd()
 {